Cardiovascular magnetic resonance determinants of ventricular arrhythmic events after myocardial infarction

Predicting postinfarct ventricular tachycardia by integrating cardiac MRI and advanced computational reentrant pathway analysis

BACKGROUND

Implantable cardiac defibrillator (ICD) implantation can protect against sudden cardiac death after myocardial infarction. However, improved risk stratification for device requirement is still needed.

OBJECTIVE

The purpose of this study was to improve assessment of postinfarct ventricular electropathology and prediction of appropriate ICD therapy by combining late gadolinium enhancement (LGE) and advanced computational modeling.

METHODS

ADAS 3D LV (ADAS LV Medical, Barcelona, Spain) and custom-made software were used to generate 3-dimensional patient-specific ventricular models in a prospective cohort of patients with a myocardial infarction (N = 40) having undergone LGE imaging before ICD implantation. Corridor metrics and 3-dimensional surface features were computed from LGE images. The Virtual Induction and Treatment of Arrhythmias (VITA) framework was applied to patient-specific models to comprehensively probe the vulnerability of the scar substrate to sustaining reentrant circuits. Imaging and VITA metrics, related to the numbers of induced ventricular tachycardias and their corresponding round trip times (RTTs), were compared with ICD therapy during follow-up.

RESULTS

Patients with an event (n = 17) had a larger interface between healthy myocardium and scar and higher VITA metrics. Cox regression analysis demonstrated a significant independent association with an event: interface (hazard ratio [HR] 2.79; 95% confidence interval [CI] 1.44-5.44; P < .01), unique ventricular tachycardias (HR 1.67; 95% CI 1.04-2.68; P = .03), mean RTT (HR 2.14; 95% CI 1.11-4.12; P = .02), and maximum RTT (HR 2.13; 95% CI 1.19-3.81; P = .01).

CONCLUSION

A detailed quantitative analysis of LGE-based scar maps, combined with advanced computational modeling, can accurately predict ICD therapy and could facilitate the early identification of high-risk patients in addition to left ventricular ejection fraction.

Variations in threshold values for border zone and dense scar produce significant changes in scar parameters obtained by ADAS-3D

BACKGROUND

ADAS-3D software elaborates cardiac magnetic resonance (CMR) images to obtain a quantitative evaluation of dense scar and border zone (BZ), including BZ channels, which can be useful for ventricular tachycardia ablation and risk stratification. However, most prior reports with ADAS-3D used flexible thresholds (60% ± 5% and 40% ± 5% of maximum pixel signal intensity) to define dense scar and BZ. The impact of such variations of the threshold values on the measurements obtained with ADAS-3D is unknown.

OBJECTIVE

This study aimed to quantify the degree of change in ADAS-3D measurements when different thresholds for dense scar and BZ are employed.

METHODS

A single-center retrospective observational cohort study including 87 consecutive patients with previous myocardial infarction who underwent CMR was conducted. ADAS-3D software semiautomatically processed CMR sequences. We compared the scar measurements obtained with the 9 possible combinations of thresholds (55%/60%/65% and 35%/40%/45% of maximum pixel signal intensity).

RESULTS

The overall comparison between thresholds showed highly significant differences (P < .001) in all scar parameters. Not a single patient maintained the same number of BZ channels with all the thresholds settings. A percentage difference of up to 200% in BZ channel numbers and channel mass was observed in all 36 comparisons. An absolute difference of up to 10 channels was also recorded. Of note, the highest median channel mass (obtained with the thresholds 35-65) was 59-fold higher compared with the lowest one (obtained with the 45-55 cutoffs).

CONCLUSION

Variations in threshold values result in statistically significant and high-magnitude changes in the quantification of scar parameters by ADAS-3D.

Role of Nuclear Imaging in Cardiac Stereotactic Body Radiotherapy for Ablation of Ventricular Tachycardia

Ventricular tachycardia (VT) is a life-threatening arrhythmia common in patients with structural heart disease or nonischemic cardiomyopathy. Many VTs originate from regions of fibrotic scar tissue, where delayed electrical signals exit scar and re-enter viable myocardium. Cardiac stereotactic body radiotherapy (SBRT) has emerged as a completely noninvasive alternative to catheter ablation for the treatment of recurrent or refractory ventricular tachycardia. While there is no common consensus on the ideal imaging workflow, therapy planning for cardiac SBRT often combines information from a plurality of imaging modalities including MRI, CT, electroanatomic mapping and nuclear imaging. MRI and CT provide detailed anatomic information, and late enhancement contrast imaging can indicate regions of fibrosis. Electroanatomic maps indicate regions of heterogenous conduction voltage or early activation which are indicative of arrhythmogenic tissue. Some early clinical adopters performing cardiac SBRT report the use of myocardial perfusion and viability nuclear imaging to identify regions of scar. Nuclear imaging of hibernating myocardium, inflammation and sympathetic innervation have been studied for ventricular arrhythmia prognosis and in research relating to catheter ablation of VT but have yet to be studied in their potential applications for cardiac SBRT. The integration of information from these many imaging modalities to identify a target for ablation can be challenging. Multimodality image registration and dedicated therapy planning tools may enable higher target accuracy, accelerate therapy planning workflows and improve patient outcomes. Understanding the pathophysiology of ventricular arrhythmias, and localizing the arrhythmogenic tissues, is vital for successful ablation with cardiac SBRT. Nuclear imaging provides an arsenal of imaging strategies to identify regional scar, hibernation, inflammation, and sympathetic denervation with some advantages over alternative imaging strategies.

Personalized pulmonary vein isolation with very high-power short-duration lesions guided by left atrial wall thickness: the QDOT-by-LAWT randomized trial

AIMS

Pulmonary vein isolation (PVI) for paroxysmal atrial fibrillation (PAF) using very high-power short-duration (vHPSD) radiofrequency (RF) ablation proved to be safe and effective. However, vHPSD applications result in shallower lesions that might not be always transmural. Multidetector computed tomography-derived left atrial wall thickness (LAWT) maps could enable a thickness-guided switching from vHPSD to the standard-power ablation mode. The aim of this randomized trial was to compare the safety, the efficacy, and the efficiency of a LAWT-guided vHPSD PVI approach with those of the CLOSE protocol for PAF ablation (NCT04298177).

METHODS AND RESULTS

Consecutive patients referred for first-time PAF ablation were randomized on a 1:1 basis. In the QDOT-by-LAWT arm, for LAWT ≤2.5 mm, vHPSD ablation was performed; for points with LAWT > 2.5 mm, standard-power RF ablation titrating ablation index (AI) according to the local LAWT was performed. In the CLOSE arm, LAWT information was not available to the operator; ablation was performed according to the CLOSE study settings: AI ≥400 at the posterior wall and ≥550 at the anterior wall. A total of 162 patients were included. In the QDOT-by-LAWT group, a significant reduction in procedure time (40 vs. 70 min; P < 0.001) and RF time (6.6 vs. 25.7 min; P < 0.001) was observed. No difference was observed between the groups regarding complication rate (P = 0.99) and first-pass isolation (P = 0.99). At 12-month follow-up, no significant differences occurred in atrial arrhythmia-free survival between groups (P = 0.88).

CONCLUSION

LAWT-guided PVI combining vHPSD and standard-power ablation is not inferior to the CLOSE protocol in terms of 1-year atrial arrhythmia-free survival and demonstrated a reduction in procedural and RF times.

Assessing left atrial intramyocardial fat infiltration from computerized tomography angiography in patients with atrial fibrillation

AIMS

Epicardial adipose tissue might promote atrial fibrillation (AF) in several ways, including infiltrating the underlying atrial myocardium. However, the role of this potential mechanism has been poorly investigated. The aim of this study is to evaluate the presence of left atrial (LA) infiltrated adipose tissue (inFAT) by analysing multi-detector computer tomography (MDCT)-derived three-dimensional (3D) fat infiltration maps and to compare the extent of LA inFAT between patients without AF history, with paroxysmal, and with persistent AF.

METHODS AND RESULTS

Sixty consecutive patients with AF diagnosis (30 persistent and 30 paroxysmal) were enrolled and compared with 20 age-matched control; MDCT-derived images were post-processed to obtain 3D LA inFAT maps for all patients. Volume (mL) and mean signal intensities [(Hounsfield Units (HU)] of inFAT (HU -194; -5), dense inFAT (HU -194; -50), and fat-myocardial admixture (HU -50; -5) were automatically computed by the software. inFAT volume was significantly different across the three groups (P = 0.009), with post-hoc pairwise comparisons showing a significant increase in inFAT volume in persistent AF compared to controls (P = 0.006). Dense inFAT retained a significant difference also after correcting for body mass index (P = 0.028). In addition, more negative inFAT radiodensity values were found in AF patients. Regional distribution analysis showed a significantly higher regional distribution of LA inFAT at left and right superior pulmonary vein antra in AF patients.

CONCLUSION

Persistent forms of AF are associated with greater degree of LA intramyocardial adipose infiltration, independently of body mass index. Compared to controls, AF patients present higher LA inFAT volume at left and right superior pulmonary vein antra.

Impact of Cardiac Magnetic Resonance to Arrhythmic Risk Stratification in Nonischemic Cardiomyopathy

Left ventricular ejection fraction-based arrhythmic risk stratification in nonischemic cardiomyopathy (NICM) is insufficient and has led to the failure of primary prevention implantable cardioverter defibrillator trials, mainly due to the inability of selecting patients at high risk for sudden cardiac death (SCD). Cardiac magnetic resonance offers unique opportunities for tissue characterization and has gained a central role in arrhythmic risk stratification in NICM. The presence of myocardial scar, denoted by late gadolinium enhancement, is a significant, independent, and strong predictor of ventricular arrhythmias and SCD with high negative predictive value. T1 maps and extracellular volume fraction, which are able to quantify diffuse fibrosis, hold promise as complementary tools but need confirmatory results from large studies.

Twenty-five years of research in cardiac imaging in electrophysiology procedures for atrial and ventricular arrhythmias

Catheter ablation is nowadays considered the treatment of choice for numerous cardiac arrhythmias in different clinical scenarios. Fluoroscopy has traditionally been the primary imaging modality for catheter ablation, providing real-time visualization of catheter navigation. However, its limitations, such as inadequate soft tissue visualization and exposure to ionizing radiation, have prompted the integration of alternative imaging modalities. Over the years, advancements in imaging techniques have played a pivotal role in enhancing the safety, efficacy, and efficiency of catheter ablation procedures. This manuscript aims to explore the utility of imaging, including electroanatomical mapping, cardiac computed tomography, echocardiography, cardiac magnetic resonance, and nuclear cardiology exams, in helping electrophysiology procedures. These techniques enable accurate anatomical guidance, identification of critical structures and substrates, and real-time monitoring of complications, ultimately enhancing procedural safety and success rates. Incorporating advanced imaging technologies into routine clinical practice has the potential to further improve clinical outcomes of catheter ablation procedures and pave the way for more personalized and precise ablation therapies in the future.

Post-myocardial infarction fibrosis: Pathophysiology, examination, and intervention

Cardiac fibrosis plays an indispensable role in cardiac tissue homeostasis and repair after myocardial infarction (MI). The cardiac fibroblast-to-myofibroblast differentiation and extracellular matrix collagen deposition are the hallmarks of cardiac fibrosis, which are modulated by multiple signaling pathways and various types of cells in time-dependent manners. Our understanding of the development of cardiac fibrosis after MI has evolved in basic and clinical researches, and the regulation of fibrotic remodeling may facilitate novel diagnostic and therapeutic strategies, and finally improve outcomes. Here, we aim to elaborate pathophysiology, examination and intervention of cardiac fibrosis after MI.

Preventive substrate ablation in chronic post-myocardial infarction patients with high-risk scar characteristics for ventricular arrhythmias: rationale and design of PREVENT-VT study

BACKGROUND

Recent studies showed that an early strategy for ventricular tachycardia (VT) ablation resulted in reduction of VT episodes or mortality. Cardiac magnetic resonance (CMR)-derived border zone channel (BZC) mass has proved to be a strong non-invasive predictor of VT in post-myocardial infarction (MI). CMR-guided VT substrate ablation proved to be safe and effective for reducing sudden cardiac death (SCD) and VA occurrence.

METHODS

PREVENT-VT is a prospective, randomized, multicenter, and controlled trial designed to evaluate the safety and efficacy of prophylactic CMR-guided VT substrate ablation in chronic post-MI patients with CMR-derived arrhythmogenic scar characteristics. Chronic post-MI patients with late gadolinium enhancement (LGE) CMR will be evaluated. CMR images will be post-processed and the BZC mass measured: patients with a BZC mass > 5.15 g will be eligible. Consecutive patients will be enrolled at 3 centers and randomized on a 1:1 basis to undergo a VT substrate ablation (ABLATE arm) or optimal medical treatment (OMT arm). Primary prevention ICD will be implanted following guideline recommendations, while non-ICD candidates will be implanted with an implantable cardiac monitor (ICM). The primary endpoint is a composite outcome of sudden cardiac death (SCD) or sustained monomorphic VT, either treated by an ICD or documented with ICM. Secondary endpoints are procedural safety and efficiency outcomes of CMR-guided ablation.

DISCUSSION

In some patients, the first VA episode causes SCD or severe neurological damage. The aim of the PREVENT-VT is to evaluate whether primary preventive substrate ablation may be a safe and effective prophylactic therapy for reducing SCD and VA occurrence in patients with previous MI and high-risk scar characteristics based on CMR.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT04675073, registered on January 1, 2021.

Analysis of Three-Dimensional Scar Architecture and Conducting Channels by High-Resolution Contrast-Enhanced Cardiac Magnetic Resonance Imaging in Chagas Heart Disease

Background:

We aimed to describe the morphology of the border zone of viable myocardium surrounded by scarring in patients with Chagas heart disease and study their association with clinical events.

Methods:

Adult patients with Chagas heart disease (n=22; 55% females; 65.5 years, SD 10.1) were included. Patients underwent high-resolution contrast-enhanced cardiac magnetic resonance using myocardial delayed enhancement with postprocessing analysis to identify the core scar area and border zone channels number, mass, and length. The association between border zone channel parameters and the combined end-point (cardiovascular mortality or internal cardiac defibrillator implantation) was tested by multivariable Cox proportional hazard regression analyses. The significance level was set at 0.05. Data are presented as the mean (standard deviation [SD]) or median (interquartile range).

Results:

A total of 44 border zone channels (1[1-3] per patient) were identified. The border zone channel mass per patient was 1.25 (0.48-4.39) g, and the extension in layers of the border zone channels per patient was 2.4 (1.0-4.25). Most border zone channels were identified in the midwall location. Six patients presented the studied end-point during a mean follow-up of 4.9 years (SD 1.6). Border zone channel extension in layers was associated with the studied end-point independent from left ventricular ejection fraction or fibrosis mass (HR=2.03; 95% CI 1.15-3.60).

Conclusions:

High-resolution contrast-enhanced cardiac magnetic resonance can identify border zone channels in patients with Chagas heart disease. Moreover, border zone channel extension was independently associated with clinical events.

The effect of left atrial wall thickness and pulmonary vein sizes on the acute procedural success of atrial fibrillation ablation

Nowadays, a novel contact-force guided ablation technique is used for enclosing pulmonary veins in patients with atrial fibrillation (AF). We sought to determine whether left atrial (LA) wall thickness (LAWT) and pulmonary vein (PV) dimensions, as assessed by cardiac CT, could influence the success rate of first-pass pulmonary vein isolation (PVI). In a single-center, prospective study, we enrolled consecutive patients with symptomatic, drug-refractory AF who underwent initial radiofrequency catheter ablation using a modified CLOSE protocol. Pre-procedural CT was performed in all cases. Additionally, the diameter and area of the PV orifices were obtained. A total of 1034 LAWT measurements and 376 PV area measurements were performed in 94 patients (mean CHA2DS2-VASc score 2.1 ± 1.5, mean age 62.4 ± 12.6 years, 39.5% female, 38.3% persistent AF). Mean procedure time was 81.2 ± 19.3 min. Complete isolation of all PVs was achieved in 100% of patients. First-pass isolation rate was 76% and 71% for the right-sided PVs and the left-sided PVs, respectively. No difference was found regarding comorbidities and imaging parameters between those with and without first-pass isolation. LAWT (mean of 11 regions or separately) had no effect on the acute procedural outcome on logistic regression analysis (all p ≥ 0.05). Out of all assessed parameters, only RSPV diameter was associated with a higher rate of successful right-sided first pass isolation (OR 1.01, p = 0.04). Left atrial wall thickness does not have an influence on the acute procedural success of PVI using ablation index and a standardized ablation protocol. RSPV diameter could influence the probability of right sided first-pass isolation.

Advances in Clinical Cardiology 2021: A Summary of Key Clinical Trials

INTRODUCTION

Over the course of 2021, numerous key clinical trials with valuable contributions to clinical cardiology were published or presented at major international conferences. This review seeks to summarise these trials and reflect on their clinical context.

METHODS

The authors reviewed clinical trials presented at major cardiology conferences during 2021 including the American College of Cardiology (ACC), European Association for Percutaneous Cardiovascular Interventions (EuroPCR), European Society of Cardiology (ESC), Transcatheter Cardiovascular Therapeutics (TCT), American Heart Association (AHA), European Heart Rhythm Association (EHRA), Society for Cardiovascular Angiography and Interventions (SCAI), TVT-The Heart Summit (TVT) and Cardiovascular Research Technologies (CRT). Trials with a broad relevance to the cardiology community and those with potential to change current practice were included.

RESULTS

A total of 150 key cardiology clinical trials were identified for inclusion. Interventional cardiology data included trials evaluating the use of new generation novel stent technology and new intravascular physiology strategies such as quantitative flow ratio (QFR) to guide revascularisation in stable and unstable coronary artery disease. New trials in acute coronary syndromes focused on shock, out of hospital cardiac arrest (OOHCA), the impact of COVID-19 on ST-elevation myocardial infarction (STEMI) networks and optimal duration/type of antiplatelet treatment. Structural intervention trials included latest data on transcatheter aortic valve replacement (TAVR) and mitral, tricuspid and pulmonary valve interventions. Heart failure data included trials with sodium-glucose cotransporter 2 (SGLT2) inhibitors, sacubitril/valsartan and novel drugs such as mavacamten for hypertrophic cardiomyopathy (HCM). Prevention trials included new data on proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors. In electrophysiology, new data regarding atrial fibrillation (AF) screening and new evidence for rhythm vs. rate control strategies were evaluated.

CONCLUSION

This article presents a summary of key clinical cardiology trials published and presented during the past year and should be of interest to both practising clinicians and researchers.